Piypite

(repeating unit)K₂Cu₂O(SO₄)₂IMA symbolPiy^[1]Strunz classification7.BC.40Crystal systemTetragonalCrystal classPyramidal (4)
H-M symbol: (4)Space groupI4Unit cella = 13.6 Å, c = 4.95 Å; Z = 2IdentificationColorEmerald-green, dark green, blackCrystal habitAcicular crystals elongated along [001], square cross section, commonly hollow; also as mosslike aggregatesCleavagePerfect, parallel to elongationTenacityBrittleMohs scale hardness2.5LusterVitreous to greasyStreakYellowish greenDiaphaneityTransparent to translucentSpecific gravity3.0 - 3.1Optical propertiesUniaxial (+)Refractive indexn_ω = 1.583 n_ε = 1.695Birefringenceδ = 0.112PleochroismDistinct; O = pale green, yellowish green; E = deep green, pale yellowish greenSolubilitySoluble in water, leaves residueReferences^[2][3][4][5]

Piypite is a rare potassium, copper sulfate mineral with formula: K₂Cu₂O(SO₄)₂. It crystallizes in the tetragonal system and occurs as needlelike crystals and masses. Individual crystals are square in cross-section and often hollow. It is emerald green to black in color with a vitreous to greasy luster.^[3][4]

It was first described in 1982 for an occurrence in the Main Fracture of the Tolbachik volcano, Kamchatka Oblast, Russia. It has also been reported from Mount Vesuvius, Italy, and in a slag deposit in the Bad Ems District in the Rhineland-Palatinate, Germany.^[3][2] Piypite occurs as a sublimate phase in a fumarole environment. Associated minerals include halite, sylvite, langbeinite, tenorite, hematite, tolbachite, dolerophanite, urusovite, aphthitalite, ponomarevite, cotunnite, chalcocyanite, sofiite, euchlorine, averievite, fedotovite, alarsite, alumoklyuchevskite, nabokoite and lammerite at the type locality in Kamchatka. On Vesuvius, it occurs with paratacamite.^[3]

References